Jan 1, 2008 12:00 PM
An overview of the applications of diesel electric hybrid technology by truck, engine, and equipment manufacturers to decrease fuel consumption, reduce carbon dioxide emissions, and power vehicle electrical systems while the engine is off was the subject of The Rise of Hybrids workshop held during the annual Foodservice Distribution Conference & Expo in Louisville, Kentucky.
Participating in the workshop were Josh Lepage, sales manager of product integration for International Truck and Engine, and Ignacio Aguerrevere, Carrier Transicold's marketing and product development director, Truck, Trailer and Rail - Americas.
The two explained that basically, diesel electric hybrid technology combines a diesel engine and an electric generator for power. After that, all components are electrically driven for maximum performance and reliability.
In the case of International's medium duty hybrids, Lepage said the hybrid electric system adds the ability to augment engine torque with electrical torque. The system recovers energy normally lost during braking with regenerative braking and stores this energy in the batteries to assist the vehicle during the next initial vehicle launch from a complete stop.
While braking, torque passing through the transmission turns the system's motor/generator drive unit into a generator to recharge the hybrid electric system's Lithium Ion batteries.
When pulling away, the system uses the motor/generator unit's electric torque to get the vehicle moving. Once up to speed, the diesel engine blends horsepower and torque to maintain desired road speed.
The hybrid electric system automatically switches to diesel power as demand is requested by the driver. This occurs based on vehicle weight and the speed demanded.
“Diesel electric hybrid vehicles can improve fuel economy up to 40 percent compared to traditional diesel engines,” said Lepage, “but there is a price-tag that comes with this technology. Currently, that gap is pretty large, similar to the introduction of the hybrid technology with automobiles. Once commercial truck manufacturers reduce cost through the manufacturing process, the price gap will shrink, making hybrid trucks more affordable.”
To help with this, in 2005 the federal government passed the Energy Policy Act that provides federal tax credits for purchasers of hybrid vehicles. The credit amount depends on the vehicle weight class, its fuel economy relative to an equivalent conventional vehicle, and the incremental cost — the amount by which the manufacturer's suggested retail price of the hybrid exceeds that of a comparable vehicle.
For a vehicle with a gross vehicle weight rating of more than 26,000 pounds that achieves an increase of 30 percent incremental fuel economy, there is a $9,000 tax credit, said Lepage. With a 40 percent or greater fuel economy increase, the tax credit becomes $12,000. “This is a huge opportunity.”
Lepage said there are 21 states that have legislative funding available that will pay up to 80 percent in fuel savings. “Check with your local state agency or its website to see what is available.”
With the introduction of new legislative funding, he said, “more states can assist in off-setting the hybrid acquisition cost, closing the gap realizing immediate return on investment of the hybrid technology.”
In his portion of the workshop, Carrier Transicold's Aguerrevere said that because hybrid diesel electric refrigeration units optimize performance throughout an application, they provide a number of advantages compared to conventional diesel mechanical refrigeration systems.
By way of example, he said Carrier Transicold's Deltek hybrid diesel electric system has a simplified design that features a sealed cooling-only refrigeration system, electric heating, and an electric-driven sealed compressor. The compressor only runs in the cooling mode, extending its life compared to conventional systems.
In heating mode, the compressor is not used. Instead, the system uses electric heating, which is more efficient than conventional hot gas, consuming less fuel and producing fewer emissions.
A built-in electric standby capability further reduces fuel consumption, exhaust emissions, and noise when the trailers are parked with access to an AC power supply.
The hybrid system has fewer parts and service items, said Aguerrevere, as it does away with such things as dampers, clutches, drive belts, and idler pulleys commonly used in conventional refrigeration. “This increases reliability, performance, and life while reducing maintenance and noise.”
In addition, he said hybrid diesel electric refrigeration systems are adaptable for use with natural refrigerants. Plus, they require about half the refrigerant charge of conventional systems.
Looking ahead at the future of hybrid refrigeration systems, Aguerrevere foresees:
More efficient sealed compression technologies.
The use of natural refrigerants.
Electric power storage.
The ability to share power with other hybrid systems.
The use of alternative power sources such as fuel cells, cleaner fuels, and renewable fuels.
Higher reliability, life, performance, and environmental benefits.
Lower cost of ownership.
The time may come, he said, when there is a complete vehicle hybrid system that encompasses the tractor, trailer, auxiliary power units, refrigeration systems, trailer accessories, and an electric grid.
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